One of conventional image projectors is described in "NATIONAL CONVENTION RECORD, 1985 of THE INSTITUTE OF ELECTRONICS AND COMMUNICATION ENGINEERS OF JAPAN". The image projector comprises a semiconductor laser head having two semiconductor lasers which produce light beams to be synthesized therein, first mirror for reflecting the light beams in a predetermined direction, a liquid crystal light valve (called "liquid crystal panel" hereinafter) in which a light transmissive pattern is formed in accordance with the scanning of the light beams on the one surface thereof, a halogen lamp from which light radiates to irradiate the other surface of the liquid crystal panel, second mirror for projecting the light reflected from the liquid crystal light panel on a screen, and a photoconductor drum to be exposed to the reflected light from the panel to produce a latent image thereon.
In operation, the light beams modulated by image signals are produced from the semiconductor laser head so that a light transmissive pattern is formed in the liquid crystal layer of the liquid crystal panel in accordance with the scanning of the modulated light beams on the scanning surface thereof by the first mirror. The liquid crystal panel is radiated on the one surface thereof so that light is reflected therefrom in accordance with the light transmissive pattern formed in the liquid crystal layer. As a result, the magnified image is displayed on the screen in accordance with the projecting of the reflected light from the panel by the second mirror. On the other hand, the photoconductor drum is exposed to the reflected light from the panel to produce a latent image thereon. The latent image thus formed is developed by use of toners. The developed toner image is transferred to a recording medium at a transferred stage. A printed image is obtained on the recording medium after finishing a fixed process at the fixed means.
According to an image projector mentioned above, the construction thereof is relatively simple as compared to, for instance, an image projector making use of a cathod ray tube (called "CRT" hereinafter) and an image having a higher resolution is produced as compared to, for instance, an image projector making use of CRT or matrix electrodes.
In the conventional image projector, however, the scanning of a liquid crystal panel is not performed at a high speed as expected because the liquid crystal panel is scanned by dots each corresponding to a picture element.
Further, one of conventional liquid crystal light shutters is described in "INTERNATIONAL SYMPOSIUM DIGEST of TECHNICAL PAPERS. Vol. XVI, 1985" in SOCIETY INFORMATION DISPLAY which was held on Apr. 30 to May 2, 1985 in Orlando, Fla. The liquid crystal light shutter which is applied to an electrophotographic recording apparatus including a photoconductor drum producing a latent image thereon comprises an upper glass substrate on which signal electrodes are provided, a lower glass substrate on which common electrode is provided, a liquid crystal layer positioned between the upper and lower glass substrates, and upper and lower polarizers provided on the other surfaces of the upper and lower glass substrates respectively. Liquid crystals for the liquid crystal layer are of ferroelectric liquid crystal material which shows a chiral smectic phase. In the chiral smectic phase, the liquid crystals have a helical structure and the molecules have spontaneous polarizations perpendicular to the axes thereof.
According to a liquid crystal light shutter mentioned above, a response time is improved as fast as 0.25 ms because the spontaneous polarizations align along upward and downward directions depending upon the two directions of electric fields each produced by positive and negative voltages applied between the respective signal electrodes and the common electrode. In addition, the printing speed is relatively high for the reason why the linearly modulated light is produced from the liquid crystal light shutter which is irradiated is exposed to te linearly modulated light to produce a latent image thereon.
In the conventional liquid crystal light shutter making use of ferroelectric liquid crystals showing a chiral smectic phase, however, a response time is difficult to be improved at the rate of less than 0.25 ms due to the limitation of the switching speed of the spontaneous polarizations thereof. Further, a circuit for driving signal electrodes in accordance with image signals is complicated for the reason why the signal electrode array of, for instance, 1024 picture elements must be driven simultaneously because the alignment of the spontaneous polarizations disappears upon the turning off of the voltage applied between the respective signal electrodes and the common electrode. Still further, it is required to apply a voltage as high as +30 V, or -30 V in accordance with the image signals to the signal electrodes in the liquid crystal light shutter.